An internal combustion engine employs an inlet manifold to distribute an air/fuel mixture into the cylinders of the engine. The mixture is drawn into the combustion chambers of the engine by a vacuum created therein by piston movement during the downward “induction” stroke of each cylinder. The induction of air/fuel mixtures into an internal combustion engine is a complicated phenomenon, one problem being to provide uniform air/fuel mixtures to each cylinder under all operating conditions.
There have been many attempts to resolve this particular problem. One method has been to employ a separate independent manifold to each cylinder. However, such an arrangement is often restricted to race engines as the cost of manufacture is significant for everyday road cars. For many everyday road cars, a single plane manifold thus remains in use serving all cylinders or, in some cases, a two-plane manifold is used, each manifold serving only half of the total number of cylinders. These types of manifolds exhibit a tendency for one cylinder to “rob” the air/fuel mixture from another cylinder.
Further, the design of an intake manifold can effect the torque and power outputs of a particular engine. Torque is required low down in the engine speed while power is required in the upper end. In the prior art solutions, designing a manifold which provides low down torque sacrifices high end power and vice versa. In an attempt to resolve these opposing requirements, some modern vehicles now incorporate an intake manifold whose configuration “changes” according to the operating conditions of the engine. These are often referred to as dual-length or variable intake manifolds. Once again, however, such designs are relatively costly to manufacture.